In the art of machines for slitting webs or sheets of metal or other materials, it is common to use a set of upper and lower rotary shafts or arbors each of which supports a series of circular slitting knives. The knives are spaced axially on each arbor by spacing collars to obtain predetermined axial spaces between adjacent knives. In order to obtain precision spacing between adjacent knives, flat annular shims are inserted between the spacing collars and the knies or between adjacent spacing collars. Usually, the shims are die cut from thin plastic sheet material, but the shims may also be constructed of metal in order to be temporarily retained by magnetics recessed within the spacing collars, for example, as disclosed in U.S. Pat. No. 4,195,542.
It is well known that substantial set-up time is required to assemble a set of rotary slitter knives on a pair of arbors with the use of spacers and shims and to obtain precision spacing between adjacent knives. More precise spacing has been obtained in recent years by the use of shimless systems which eliminate the need for the thin plastic or metal shims. In a shimless system, a series of spacing collars are ground with precise axial widths, for example, within tolerances of plus or minus one micron (0.000040 inch). However, this precision grinding and lapping of the spacer collars increases the cost of the collars. Furthermore, the precision spacing collars for a shimless set-up must be carefully handled to avoid any possible damage to the precision parallel surfaces on the spacer collars.
Another form of spacing the rotary or circular knives on each arbor of a slitting machine is disclosed in U.S. Pat. No. 2,804,134. In this patent, adjacent slitter knives are spaced on the arbor by a set of rods or pins which are precisely ground to length or diameter. The rods or pins are carried by a resilient stripper ring which has a radial cut so that the stripper ring may be deformed to an open position for mounting the ring on the shaft or arbor. The lengths of the rods or pins correspond to the desired spacing between adjacent slitter knives so that opposite ends of each rod or pin engage or contact the adjacent slitter knives. In order for the slitting machine to slit strips of various widths, there must be either a large inventory of the resilient stripper rings or the stripper rings must be made for each set-up.